1. Field of the Invention
The present invention relates to a focus adjustment unit and an optical scanning microscope.
This application is based on Japanese Patent Applications Nos. 2007-240103 and 2007-240104, the contents of which are incorporated herein by reference.
2. Description of Related Art
There has been a microscope in which a positive refractive power optical element and a negative refractive power optical element are disposed between a light source and an objective lens and the physical distance between these optical elements is changed to change the working distance of the objective lens (see Japanese Unexamined Patent Application, Publication No. 2005-70477, for example).
Also disclosed is a microscope in which an adaptor lens is detachably attached to a finite distance objective lens (see Japanese Unexamined Patent Application, Publication No. 2006-79000, for example). In the microscope, a small-diameter, finite distance objective lens is combined with an adaptor lens, and the working distance of the objective lens is changed by moving the adaptor lens in the optical axis direction.
There has also been a microscope having a detachable, finite distance objective lens (see Japanese Unexamined Patent Application, Publication No. 2006-139181, for example). In the microscope, a finite distance objective lens is combined with an imaging lens, and the working distance of the objective lens is changed by moving the imaging lens in the optical axis direction.
The patent publication disclosures about the above microscopes, however, do not describe at all the positional relationship of the objective lens and the imaging lens with the optical system that shifts the focal point, and it is conceivable that moving a lens that is part of the optical system in the optical axis direction in order to change the working distance of the objective lens may disadvantageously change the observation magnification greatly if no consideration is given to the positional relationship of the optical system with the objective lens and the imaging lens.